Oppo 105D versus Benchmark Dac 2 ?

I think a better difference would be with Mytek or Schiit.

Both have very good Redbook playback.

If you need to play silver disks and/or video, then the OPPO. If you don't and need analog preamplifier functions, the DAC 2 or the new DAC 3. With either you can listen to Redbook CDs or higher resolution formats to a very high standard indeed. Why pay more? 

Just like the world of computers, the chips change, get higher resolution, and then new models come out. I've had OPPO products for a long time. Neither company comes out with a new product until the key chips get better.